Given that Crataegus is such a weed in my part of the world, I would have thought that all you had to do to germinate them was chuck the seeds on the ground! Although one of these weed sites says they are spread by birds, so maybe something in the bird digestive system helps them germinate:
https://vro.agriculture.vic.gov.au/dpi/vro/vrosite.nsf/pages/weeds_shrubs_hawthorn
https://weeds.dpi.nsw.gov.au/Weeds/Hawthorn